1. Field of the Invention
The present invention relates to an overhead submerged arc welding process wherein a flux for submerged arc welding is pressed onto the portion to be welded from the underside of the welding line of the plates to be welded and the welding is effected while feeding a consumable electrode from the underside of the plates to be welded.
2. Description of the Prior Art
Overhead welding has conventionally been accomplished by means of a hand welding process, a TIG welding process, a MIG welding process and a CO.sub.2 gas shielded welding process. However, such conventionally known processes have disadvantages in that the amount of deposit along the path is small, that a number of steps is required, that soundness of the weld cannot be easily obtained, and that there are environmental problems for the operators. For this reason, overhead welding has been considered not to be suited for welding relatively thick plates such as welding of the bottom shell plates in the shipbuilding industry. It has, therefore been proposed to apply the submerged welding technique which provides a large amount of welded metal over such a path. For example, there has been disclosed in an article "Automatic Welding with Flux of Tubes in Upward Position" in Welding Process (Russion Publication), No. 11 (1958), pages 19 to 23, an overhead submerged welding process which is applied for welding a pipe. According to the above mentioned reference, there is disclosed a submerged welding process using a flux hopper which supplies a circulated flux for submerged welding to the welding line and in the vicinity thereof and a consumable electrode extending through the flux hopper for effecting submerged welding from the underside of the pipe without using a backing strip, wherein the inner surface of the welding joint pipe is welded at a first place and the pipe is then rotated by 180 degrees to be welded from the upperside thereof by means of flat welding, whereupon dropping of the molten metal is prevented by the welded metal formed by the overhead submerged arc welding process even when a backing strip is not used on the inner wall of the pipe. The quality of the welded portion formed by the overhead submerged arc welding process is determined by the composition and grain size of the used flux which is supplied from the underside of the welding line, and depends on the method of supplying the flux into the groove and in the vicinity thereof, as well. In order to suitably supply the flux into and in the vicinity of the groove from the underside portion thereof, it is necessary to press the flux into the vicinity of the welding arc at a suitable pressure and to supply flesh flux as the welding is advanced and to remove the consumed and slagged flux. Smooth cyclic operations for supplying and removing the flux shall be accomplished. The overhead submerged arc welding process has not yet been practically applied for effecting abutt welding of thick plates because of various problems as exemplified in the foregoing descriptions. Accordingly, there is a demand for the development of an overhead submerged arc welding process which may be easily practiced and which provides a sound welded portion.